ODOT is facing a new reality of decreasing gas tax revenue as cars become more efficient. In response, the agency is downsizing its workforce, mostly by not replacing workers who've retired. And those retirements are coming fast and furious. About a third of the agency's highway division is eligible to retire over the next five years.

ODOT spokesman Dave Thompson said the report points out a valid concern.

"There's so much to the job that you learn by doing," he said. "And the Secretary of State pointed out that we need better planning so that we don't lose all that wonderful accrued knowledge as someone retires."

The workforce challenges come as Oregon's infrastructure is aging. The agency says hundreds of bridges will need to be replaced in the coming decades.